Hagg S A, Morse E L, Adibi S A
Am J Physiol. 1982 Jun;242(6):E407-10. doi: 10.1152/ajpendo.1982.242.6.E407.
We have previously hypothesized that increased muscle oxidation of leucine in starvation is an adaptive response to fuel deficiency in this tissue. To investigate this hypothesis further, we have measured the rates of oxidation, turnover, and plasma clearance of [1-14C]leucine in six obese subjects at rest and during 2 h of mild leg exercise. This experimental design was based on the fact that exercise has the greatest impact on energy expenditure in muscle, the principal site for leucine oxidation. Exercise produced a fourfold increase in oxygen consumption. The rate of alpha-decarboxylation of leucine was increased twofold by leg exercise, whereas there were modest decreases (13%) in the rates of turnover and plasma clearance of this amino acid. The plasma concentrations of lactate and alanine increased twofold during exercise, but plasma concentrations of leucine and other amino acids, glucose, beta-hydroxybutyrate, and insulin remained unaltered. Our data suggest that during exercise oxidation of leucine as an energy source increases, whereas the utilization of this amino acid as a substrate for protein synthesis decreases.
我们之前曾推测，饥饿状态下肌肉中亮氨酸氧化增加是该组织对燃料缺乏的一种适应性反应。为了进一步研究这一假设，我们测量了6名肥胖受试者在静息状态以及轻度腿部运动2小时期间[1-14C]亮氨酸的氧化率、周转率和血浆清除率。该实验设计基于这样一个事实，即运动对肌肉（亮氨酸氧化的主要部位）的能量消耗影响最大。运动使耗氧量增加了四倍。腿部运动使亮氨酸的α-脱羧率增加了两倍，而该氨基酸的周转率和血浆清除率略有下降（13%）。运动期间，乳酸和丙氨酸的血浆浓度增加了两倍，但亮氨酸和其他氨基酸、葡萄糖、β-羟基丁酸酯和胰岛素的血浆浓度保持不变。我们的数据表明，运动期间作为能量来源的亮氨酸氧化增加，而作为蛋白质合成底物的该氨基酸利用减少。
